feat: Heron layout model as new default (#1971)

* feat: Switch default layout model to DOCLING_LAYOUT_HERON. Update the unit test data.

Signed-off-by: Nikos Livathinos <nli@zurich.ibm.com>

* Use default layout model in model_downloader default args

Signed-off-by: Christoph Auer <cau@zurich.ibm.com>

* Use default layout model in model_downloader default args

Signed-off-by: Christoph Auer <cau@zurich.ibm.com>

* Update docling-models tag for TableFormer

Signed-off-by: Christoph Auer <cau@zurich.ibm.com>

* Update test GT

Signed-off-by: Christoph Auer <cau@zurich.ibm.com>

* Update test GT (from linux CPU)

Signed-off-by: Ubuntu <ubuntu@ip-172-31-30-253.eu-central-1.compute.internal>

* fix: Ensure that the visualisations happen on copies of the page image

Signed-off-by: Nikos Livathinos <nli@zurich.ibm.com>

* chore: Pinpoint docling-ibm-models to the fix branch for the ReadingOrderPredictor

Signed-off-by: Nikos Livathinos <nli@zurich.ibm.com>

* chore: Update uv.lock

Signed-off-by: Nikos Livathinos <nli@zurich.ibm.com>

* chore: Update tests GT to match the Heron layout model and the improved reading order model in Linux

Signed-off-by: Nikos Livathinos <nli@zurich.ibm.com>

* fix: Introduce the verify_doctags optional parameter in conversion tests to control if a doctags
comparison should take place. Skip doctags comparisons for certain tests.

Signed-off-by: Nikos Livathinos <nli@zurich.ibm.com>

* chore: Generate tests GT on Mac

Signed-off-by: Nikos Livathinos <nli@zurich.ibm.com>

* chore: Remove the pinning of the docling-ibm-models and use the release 3.9.1

Signed-off-by: Nikos Livathinos <nli@zurich.ibm.com>

---------

Signed-off-by: Nikos Livathinos <nli@zurich.ibm.com>
Signed-off-by: Christoph Auer <cau@zurich.ibm.com>
Signed-off-by: Ubuntu <ubuntu@ip-172-31-30-253.eu-central-1.compute.internal>
Co-authored-by: Christoph Auer <cau@zurich.ibm.com>
Co-authored-by: Ubuntu <ubuntu@ip-172-31-30-253.eu-central-1.compute.internal>